The proposal is to establish a versatile, modern facility for microscopy and image-processing as applied to research problems in cell biology. The facility will include a Zeiss Axiomat microscope equipped for differential interference contrast and fluorescence work, a low noise TV camera with wide-range offset and gain controller, a charge-injection camera and microchannel plate image intensifier, a frame-memory and digital image processor, video tape recorders for information storage and retrieval, and a laser illuminator and photon counter for microspectrofluorometry. These instruments will be shared by three major users. In project I the Axiomat, video controller, frame-memory and digitizer will be used to study the rapid axonal transport of small particles, according to the new Video-Enhanced-Contrast method of R.D. Allen. Both frog and rat nerve will be used. Experiments are planned to investigate the kinetics and mechanism of transport and the turnaround of transported organelles at normal and diseased nerve-endings. In project II, the image-intensifier, frame-memory and digitizer will be used to study the intracellular localization of calcium ions as indicated by the bioluminescent probe, aequorin. The focus will be on studying the role of the calcium ion as an intracellular messenger, and investigating the regulation of intracellular calcium concentration. In project III, the Axiomat will be used with laser illumination for measurements of fluorescence anistropy and recovery from photobleaching in discrete regions of cells exposed to fluorescent probes. Digital image processing of signals obtained at low light levels with the image intensifier will also be used for studies of the internalization and fate of fluorescent probes that interact with cell-surface proteins and receptors.